Ok, so if the car does reach operating temperature, and both the upper and lower radiator hoses get hot to the touch, at least you know that you have flow and that the thermostat must be operating normally.
It seems odd that neither heater core hose gets warm/hot, as usually you would have at least the inlet getting warm. So if both are cold, that means you aren't getting hot flow to the inlet hose, which in turn would obviously not let the outlet hose get hot either.
I would check any heater valves that control flow to the heater core. Sometimes the car can be equipped with a vacuum operated one, or an electric valve. When these valves go bad, flow is limited. If your car does not have one of these valves, I would start to check for any restrictions in the cooling system. You could have a bad hose that has collapsed, or a bad clogged up hose or core.
GM Dealer Technician For 18+ Years
In the automotive industry for 20+